The present invention relates to precision optical mounts used to make ultra-fine adjustments to the positions and/or angular orientations of optical components.
Adjustable mounting apparatuses are commonly used in applications, such as interferometry and holography, in which precise positioning of optical components is essential. Such optical mounts typically comprise a pair of parallel plates: a base plate, which is rigidly fixed to a supporting base or surface, and a stage plate, on which optical components, such as mirrors, lenses, diffraction gratings, prisms, beam-splitters, light sources, and lasers, are mounted. Typically, the stage plate is coupled to the base plate by one or more compressive means—usually springs—which urge the two plates together. Countering the tensioning force of the springs are multiple kinematic adjustment members, which are typically fine pitch adjuster screws that control the position of the stage plate relative to the base plate.
In the prior art, as shown in FIG. 1, the adjuster screw is threaded through the stage plate by means of a threaded bushing, wherein the pitch of bushing threads matches that of the adjuster screw. The threaded bushing is usually press fitted or adhesively bonded into a matching hole in the stage plate of the optical mount, such that the bushing cannot be removed once it is fitted into the mount. For fine resolution applications, the pitch of the adjuster screw and threaded bushing is typically 80 TPI. But in more demanding applications, in which ultra-fine resolution is needed, ultra-fine pitch of 0.10 mm may be required. While there is a need to to interchange adjuster screws of different pitches in an optical mount, however, the prior art threaded bushing does not allow this, but instead requires that the entire mount be changed, because the bushing has been irremovably fitted into the stage plate of the mount.
The present invention fulfills the need for adjuster pitch interchangeability by providing a multi-component adjuster assembly in place of the single-component bushing of the prior art. The adjuster assembly comprises a carrier bushing and an internally-threaded core bushing that fits snuggly inside the carrier bushing. The carrier bushing is fixedly fitted into the hole in the stage plate, and the core bushing slides inside it. The core bushing is irrotatably locked into position within the carrier bushing by conjugate key-keyway structures on the carrier and core bushings. Alternately, the core bushing can have exterior threading that threads into interior threading in the carrier bushing. While the carrier bushing remains in the stage plate of the optical mount, the core bushing can be removed and replaced with another core bushing having a different thread pitch. In this way, the same mount may be used with either fine adjuster screws (e.g., 80 TPI) or ultra-fine adjuster screws (e.g., 0.10 mm) by simply interchanging core bushings having the corresponding pitches.